Recently, in semiconductor packages in which a semiconductor element is enclosed, the heat generation rate has been increasing as the operation frequency and the wiring density of the semiconductor element increase and the density of wiring increases, and there is a need to securely dissipate the generated heat and to effectively reduce the thermal resistance. Moreover, as a semiconductor package which is superior in the convenience of additional installation, version upgrading, and maintenance etc. of electronic equipment after it is brought into operation, semiconductor packages of an LGA (Land Grid Array) structure in which thin plate-shaped electrodes are arranged in a grid-like pattern on the surface are widely used.
FIG. 1 is a sectional view of a conventional semiconductor package of an LGA structure.
The semiconductor package 10 includes a wiring board 11 in the lower face of which thin plate-shaped electrodes are disposed, a semiconductor element 12 to which I/O terminals 14 are attached, a heat spreader 17 which dissipates heat generated in the semiconductor element 12, a spacer 16 which supports the heat spreader 17, where the semiconductor element 12 and the heat spreader 17 are joined by a joining member 13, and the spacer 16, the wiring board 11, and the heat spreader 17 are bonded by an adhesive 15. In order to reduce the thermal resistivity of the semiconductor element 12, it is necessary to effectively transfer heat generated at the semiconductor element 12 to the heat spreader 17, and therefore the thickness of the joining member 13 for joining the semiconductor element 12 with the heat spreader 17 is precisely adjusted.
The semiconductor package 10, in which the wiring board 11 is displaced so as to face a socket with pins arranged in a grid-like pattern, is mounted into electronic equipment by being strongly pressed against the socket. Thus, a semiconductor package 10 of LGA structure has an advantage in that it may be attached to and detached from electronic equipment more easily and may be powered more efficiently compared with semiconductor packages including raised electrodes made up of pins and solder etc.
Incidentally, in a semiconductor package 10 of LGA structure, the registration with the socket is performed by the outer dimensions, and the semiconductor package 10 is mounted into electronic equipment by being strongly pressed against the socket. For this reason, if the wiring board 11, the heat spreader 17, and others are obliquely bonded due to the squeeze-out of the adhesive 15 or any other factor, the pressing force F from the socket will be applied leaning toward one part of the surface of the wiring board 11 posing risks of such as fracture of the wiring board 11 and breakage of the internal wiring. Further, if the adhesive 15 is squeezed out beyond the outer dimension of the semiconductor package 10, misregistrations between the semiconductor package 10 and the socket may take place resulting in connection deficiencies.
In this respect, Japanese Laid-open Patent Publications No. 2006-80297 and No. 2004-296739 describe a technique in which there is provided a step in the end face of the spacer so that the squeezed-out adhesive is accommodated therein. According to the technique described by Japanese Laid-open Patent Publications No. 2006-80297 and No. 2004-296739, since an excess adhesive will be pressed out to the end face of the spacer entering into the step, it is possible to mitigate the squeeze-out of the adhesive.
However, since the semiconductor package 10 itself is small-sized, a problem remains in that the amount of adhesive which may be accommodated in the step in the spacer end face is very small and is not enough to solve the fracture of the wiring board and the connection deficiencies due to the squeeze-out of the adhesive.